Collagen is the major structural protein of the body and recent studies have emphasized its role in other biological processes including differentiation and cell adhesion. Connective tissue abnormalities which may be related to biological properties of collagen occur throughout medicine. These include fibrotic conditions, osteoporosis, wound healing, developmental defects, and aging. Human skin fibroblasts in culture devote a considerable portion of their biosynthetic capacities to collagen production and provide a convenient means for studying the regulation of its synthesis. Collagen synthesis including type-specific synthesis and levels of modifying enzymes (lysyl hydroxylase and prolyl hydroxylase) will be studied. An attempt will be made to understand the role and level of regulatory influences including hormonal and nutritional on collagen production in these cells.